Parse your domain's SPF record, count DNS lookups, expand includes recursively, and flag common misconfigurations that cause email deliverability issues.
Sender Policy Framework (SPF) is a DNS TXT record that lists the servers allowed to send email from your domain. Receivers check it to help reject spoofed mail. A bad SPF record causes legitimate email to end up in spam — or attackers to successfully impersonate your domain. RFC 7208 caps the chain at 10 DNS lookups; exceeding that is a common failure mode.